Method for random access in wireless communication system, wireless communication system, wireless terminal, and base station unit

ABSTRACT

Random access in a wireless communication system including a base station and a wireless terminal, whereby at the wireless terminal, performing first random access scheme using a first random access preamble or second random access scheme using a second random access preamble which is received from the base station.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.12/689,639, filed on Jan. 19, 2010, now pending, which is a continuationof PCT international application No. PCT/JP2007/065745 filed on Aug. 10,2007 in Japan, the contents of each are herein wholly incorporated byreference.

FIELD

The embodiments discussed herein are related to a method for randomaccess in a wireless communication system, a wireless terminal, and abase station unit.

BACKGROUND ART

For a mobile communication system such as mobile telephones, thethird-generation scheme has started providing service through the use ofCDMA scheme. The 3GPP (3rd Generation Partnership Project) (R) has beendiscussed over the next-generation mobile communication system (LTE:Long Term Evolution) which makes communication at a higher speedpossible (see Non-Patent Document 1 below). In the project, reduction ofdelay in transmission is being discussed in addition to enhancement intransmission rate.

In the event of initiation of communication between a base station unit(evolved Node B: eNB) and a mobile station unit (User Equipment: UE)serving as a wireless terminal prepares in a mobile communicationsystem, a channel is prepared through which the UE first transmits data.The 3GPP calls this channel a random access channel (RACH) and calls acommunication starting procedure using a RACH random access (seeNon-Patent Document 2 below).

A RACH includes minimum information that causes the eNB to recognizetransmission from the UE. A RACH is used at the initiation of thecommunication and the subsequent communication uses an individualchannel (or common channel). A RACH can be shared by a number of UEsunless two or more UEs concurrently use the RACH. For the above, a RACHuses an identifier called a signature with which the eNB can identifyUEs concurrently transmitting data through the RACH.

Random access is carried out in the following four cases of: (1)transmission of first data; (2) establishment uplink synchronizationwhen downlink data arrive; (3) request of uplink data transmission whenuplink data arrive; and (4) establishment of synchronization with adestination base station when handover occurs. The direction from theeNB to the UE is defined as “downlink (DL)”, and the reverse directionis defined as “uplink (UL)”.

Here, when (1) transmission of first data or when (3) transmission ofuplink data, the UE randomly selects one signature from availablesignatures (preambles) and uses the selected signature (Contention BasedRandom Access Procedure). Accordingly, there is a possibility, howeverbeing low, of two or more UEs concurrently transmit data using the samesignature.

Conversely, the eNB allocates a dedicated signature to the UE in advancewhen (2) transmission of downlink data. A possible collision of asignature may cause an instantaneous interruption of the connection orcommunication disconnection of the communication when (4) handoveroccurs. Therefore, a dedicated signature is allocated to the UE that isthe subject of the handover (Non-contention Based Random AccessProcedure).

(a) Contention Based Random Access Procedure:

FIG. 20 illustrates an example of a random access procedure used in theabove cases (1) and (3) disclosed in the non-Patent Document 2.

Upon uplink data arrival, the UE transmits a message (Random AccessPreamble) #1-1 (uplink transmission request) containing a signaturerandomly selected to the eNB through the RACH (step S101). At that time,there is a possibility of occurrence of a contention because two or moreUEs concurrently start transmission through the use of the samesignature. However, even when a contention occurs, the eNB cannotrecognize the effective ID of each UE and cannot therefore grasp thatthe contention occurs between which UEs.

Upon receipt of the message #1-1 (the signature), the eNB reply with theresponse message (Random Access Response) #1-2 to the received message#1-1 (step S102) along with a timing advanced as synchronization signalsfor uplink communication, an uplink grant for transmission permission,and others. If a number of UEs 20 concurrently transmit requests throughthe RACH, the eNB 10 returns the response message #1-2 to the UEs 20.

Next, the UE, which receives the response message #1-2, transmits the IDof the UE itself via a message (Scheduled Transmission) #1-3 to requestthe eNB 10 to schedule UL communication to the eNB (step S103).

Upon receipt of the message #1-3, the eNB recognizes the effective ID ofthe UE (hereinafter also called a terminal ID) and thereby can graspthat the contention of the signature occurs between which UEs. If acontention occurs, the eNB transmits a message (Contention Resolution)#1-4 to the UEs in question to resolve the contention (step S104).

(b) Non-Contention Based Random Access Procedure

FIG. 21 illustrates an example of a random access procedure(Non-contention Based Random Access Procedure) used in the above cases(2) and (4) disclosed in the Non-Patent Document 2.

The eNB allocates a dedicated signature to each UE under the control ofthe eNB via a message (Random Access Preamble assignment) #2-1 inadvance (step S20).

The UE issues UL synchronization request to the eNB using the dedicatedsignature allocated by the eNB via the message #2-1. In other words, theUE transmits a message #2-2 containing a dedicated signature to the eNBthrough the RACH (step S202).

Upon receipt of the message #2-2, the eNB replies with the responsemessage #2-3 to the received message (step S203) along with a timingadvanced as synchronization signal, an uplink grant for transmissionpermission, and others.

Non-Patent Document 1: 3GPP, “Requirements for Evolved UTRA (E-UTRA) andEvolved UTRAN (E-UTRAN)”, TR25.913 V7.3.0, Release 7, March 2006

Non-Patent Document 2: 3GPP, “Evolved Universal Terrestrial Radio Access(E-UTRA) and Evolved Universal Terrestrial Radio Access Network(E-UTRAN)”, TS36.300, Release 8, V8.1.0, June 2007

As described above, since the non-Patent Document 2 examines two kindsof procedure of random access, different procedures concurrently proceedin, for example, cases of (2) establishment uplink synchronization whendownlink data arrive and (3) request of uplink data transmission whenuplink data arrive.

Since different procedures concurrently proceeding as the above requiresrespective resources (such as signature), two kinds of signature areallocated while the procedures are proceeding so that the signatures arewasted.

SUMMARY

(1) According to an aspect of the embodiments, a method includes amethod for random access in a wireless communication system including abase station unit and a wireless terminal, the method including: at thewireless terminal, detecting first information used for first randomaccess and second information used for second random access, the secondinformation being received from the base station unit; and selecting onebetween the first information and the second information.

(2) According to an aspect of the embodiments, a method includes amethod for random access in a wireless communication system including abase station unit and a wireless terminal, the method including: at thewireless terminal, receiving second information used for second randomaccess in response to generation of downlink data from the base stationunit before creating first information used for first random access inresponse to generation of uplink data destined for the base stationunit, transmitting third information, which is transmitted to the basestation unit during the first random access, to the base station unitduring or after the completion of the second random access using thesecond information.

(3) According to an aspect of the embodiments, a system includes awireless communication system including a base station unit and awireless terminal, wherein the wireless terminal selects one from firstinformation used for first random access and second information used forsecond random access, the second information being received from thebase station unit; and the base station unit releases management of theinformation that is not selected between the first information and thesecond information.

(4) According to an aspect of the embodiments, an apparatus includes awireless terminal including: creating means that creates firstinformation used for first random access to a base station unit;receiving means that receives, from the base station unit, secondinformation used for second random access to the base station unit; andselecting means that selects one between the first information and thesecond information.

(5) According to an aspect of the embodiments, an apparatus includes abase station unit including: managing means that manages firstinformation used for first random access received from a wirelessterminal and second information used for second random accesstransmitted to the wireless terminal; determining means that determines,based on third information received from the wireless terminal, oneselected by the wireless terminal between the first information and thesecond information; and controlling means that continuing random accesscorresponding to the information that the determining means determinesthat the wireless terminal selects and that carries out control based onthe third information.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a base station (eNB)according to a first embodiment;

FIG. 2 is a functional block diagram illustrating a mobile station (UE)according to the first embodiment;

FIG. 3 is a sequence diagram explaining a procedure (method) of randomaccess according to the first embodiment;

FIG. 4 is a flow diagram explaining the operation of the eNB whencarrying out the random access procedure of FIG. 3;

FIG. 5 is a flow diagram explaining the operation of the UE whencarrying out the random access procedure of FIG. 3;

FIG. 6 is a sequence diagram explaining a case in which different randomaccess procedures are concurrently proceeding;

FIG. 7 is a sequence diagram explaining a procedure (method) of randomaccess according to a second embodiment;

FIG. 8 is a flow diagram explaining the operation of the eNB whencarrying out the random access procedure of FIG. 7;

FIG. 9 is a flow diagram explaining the operation of the UE whencarrying out the random access procedure of FIG. 7;

FIG. 10 is a sequence diagram explaining a first modification to thesecond embodiment;

FIG. 11 is a sequence diagram explaining a second modification to thesecond embodiment;

FIG. 12 is a sequence diagram explaining a procedure (method) of randomaccess according to a third embodiment;

FIG. 13 is a flow diagram explaining the operation of the eNB whencarrying out the random access procedure of FIG. 10;

FIG. 14 is a flow diagram explaining the operation of the UE whencarrying out the random access procedure of FIG. 10;

FIG. 15 is a sequence explaining a procedure (method) of random accessaccording to a fourth embodiment;

FIG. 16 is a flow diagram explaining the operation of the eNB whencarrying out the random access procedure of FIG. 13;

FIG. 17 is a flow diagram explaining the operation of the UE whencarrying out the random access procedure of FIG. 13;

FIG. 18 is a sequence diagram explaining a procedure (method) of randomaccess according to a fifth embodiment;

FIG. 19 is a sequence explaining a procedure (method) of random accessaccording to a sixth embodiment;

FIG. 20 is a sequence diagram explaining a conventional procedure ofrandom access (contention based random access); and

FIG. 21 is a sequence diagram explaining a conventional procedure ofrandom access (non-contention based random access).

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be described with reference to thedrawings. Note that the embodiments are not limited to the embodimentsto be described below, but may be modified in various ways withoutdeparting from sprits and scope of the embodiments, as a matter ofcourse.

(1) First Embodiment

FIG. 1 is a functional block diagram of a base station unit (eNB)according to the first embodiment; and FIG. 2 is a functional blockdiagram of a mobile station unit (UE) according to the first embodiment.The eNB 10 and the UE 20 form a wireless communication system. Thewireless communication system can include a number of eNBs 10 and anumber of UEs 20. The configurations illustrated in FIGS. 1 and 2 arealso common to second through fourth embodiments detailed below unlessotherwise specified. In addition, the base station unit 10 of the firstembodiment assumes to be an LTE eNB which possesses a part of or theentire function of a radio network controller (RNC), but may be a basestation of a former generation of the LET (i.e., without the function ofRNC). In addition, the base station may comply with any system as longas adopting both the contention based random access procedure and thenon-contention based random access procedure.

(Description of eNB)

Focusing on the major functions, the eNB 10 illustrated in FIG. 1includes, for example, an antenna 11, a transmitting/receiving unit, abuffering unit 13, a judging unit 14, a signature managing unit 15, anda wireless resource managing unit 16.

Here, the antenna 11 receives an uplink wireless signal from the UE 20while transmits downlink wireless signal to the UE 20. The antenna 11 iscommonly used for transmitting and receiving, but alternatively anantenna for transmitting may be separated from an antenna for receiving.

The transmitting/receiving unit (transmitting means, receiving means) 12performs predetermined receiving processing on an uplink wireless signalreceived by the antenna 11 while performs predetermined transmittingprocessing on data (downlink data) from the buffering unit 13.

The receiving processing includes, for example, low-noise amplification,frequency conversion (down-conversion) to the baseband frequency, gainadjustment, demodulation by a predetermined demodulating scheme, anddecoding by a predetermined decoding scheme. The transmitting processingincludes encoding of the uplink transmission data by a predeterminedencoding scheme, modulating of the encoded data by a predeterminedmodulating scheme (such as QPSK or 16QAM), creating of a predeterminedwireless frame, frequency conversion (up-conversion) to the radiofrequency, and electric power amplification. The above wireless frame isexemplified by one conforming to OFDMA, OFDMA, or others.

The buffering unit 13 temporarily stores downlink data destined for theUE 20 under the control of the signature managing unit 15. The judgingunit (determining means) 14 has a function of determining whichsignature was selected between a random signature and a dedicatedsignature through judging, on the basis of uplink data (message)subjected to receiving processing in the transmitting/receiving unit 12,whether or not an UL synchronization request or an UL scheduling requestis issued from the UE 20.

In the first embodiment, a random signature represents a signature(first information) that the UE 20 randomly creates and a dedicatedsignature represents a signature (second information) that the eNB 10allocates (sends) to the UE 20. The detailed method for the judgmentwill be described below.

The signature managing unit (managing means) 15 manages a signature(Random Access Preamble, hereinafter also called a preamble) used forrandom access (procedure), creates a downlink message destined for theUE 20 and used for random access, and has a function of allocating andreleasing a signature for the UE 20. The release is based on the resultof the judgment by the judging unit 14.

The wireless resource managing unit 16 manages UL and DL wirelessresources (e.g. channel frequency and time (transmitting/receivingtimings)) to be used for communication (including communication whenrandom accessing) with the UE 20 and allocation of the resources. Forexample, when OFDMA is adopted, the wireless resource managing unit 16has a function to manage the mapping of a two-dimensionaltransmitting/receiving region (called a burst) defined in terms of thesub-channel frequency and the symbol time.

In addition, the wireless resource managing unit 16 has a function ascontrolling means that carries out control based on an uplink message(third information) which is received from the UE 20 during randomaccess corresponding to the signature that is not selected by the UE 20.

(Description of UE)

Focusing on the major functions, the UE 20 illustrated in FIG. 2includes, for example, an antenna 21, a transmitting/receiving unit 22,a buffering unit 23, a signature managing unit 24, an access judgingunit 25, and an identifier providing unit 26.

Here, the antenna 21 receives a downlink wireless signal from the eNB 10while transmits an uplink wireless signal to the eNB 10. Also theantenna 21 is commonly used for transmitting and receiving, butalternatively, an antenna for transmitting may be separated from anantenna for receiving.

The transmitting/receiving unit (transmitting means, receiving means) 22performs predetermined receiving processing on a downlink wirelesssignal received by the antenna 21 while performs predeterminedtransmitting processing on data (uplink data) from the buffering unit 23and on an uplink message (e.g., a Random Access Preamble and a ScheduledTransmission message) destined for an eNB via the identifier providingunit 26.

The receiving processing by the UE 20 also includes, for example,low-noise amplification, frequency conversion (down-conversion) to thebaseband frequency, gain adjustment, demodulation by a predetermineddemodulating scheme, and decoding by a predetermined decoding scheme.The transmitting processing includes encoding of the uplink transmissiondata by a predetermined encoding scheme, modulating of the encoded databy a predetermined modulating scheme (such as QPSK or 16QAM),multiplexing (mapping) of uplink data to a predetermined wireless frame,frequency conversion (up-conversion) to the radio frequency, andelectric power amplification.

The buffering unit 23 temporarily stores uplink data destined for theeNB 10 under the control of the signature managing unit 24, whichmanages a signature (Random Access Preamble) used for random accessprocessing (procedure).

The access judging unit 25 generates a predetermined message to be usedfor the random access procedure in cooperation with the signaturemanaging unit 24. In this example, the access judging unit 25 has afunction of monitoring (confirming) whether or not multiple allocationof signatures occurs, that is, whether or not a dedicated signatureallocated by the eNB 10 and a random signature randomly created by theUE 20 itself (by the signature managing unit 24) exist and in the eventof occurrence multiple allocation, determining which signature is madeto be effective.

The identifier providing unit 26 has a function of providing an uplinkmessage (e.g., a message informing of the terminal ID) which is destinedfor the eNB 10 and which is generated by the access judging unit 25 withinformation (an identifier, a flag, or the like) indicating that theuplink message also serves as a message that requests to transmit anuplink data (UL scheduling) because also uplink data is being generatedat the UE 20 or that the uplink message serves as UL synchronizationconfirmation responsive an UL synchronization requests required forreceiving downlink data because downlink data arrives at the eNB 10. TheUL synchronization confirmation is a notification (confirmationresponse) to the eNB 10 that the UE 20 secures UL synchronization due tocorrect receiving UL timing information from the eNB 10.

(Description of a Random Access Procedure)

Hereinafter, detailed description will now be made in relation to anoperation (a random access procedure) in a wireless communication systemof the first embodiment having the above configuration with reference toFIGS. 3 through 5. FIG. 3 is a sequence diagram explaining the randomaccess procedure (method) of the first embodiment; FIG. 4 is a flowdiagram explaining the operation of the eNB 10 when the random accessprocedure of the first embodiment is being carried out; and FIG. 5 is aflow diagram explaining the operation of the UE 20 when the randomaccess procedure of the first embodiment is being carried out.

Hereinafter, similarly to the description of FIGS. 20 and 21, themessages with the reference numbers #1-1 through #1-4 representsmessages originally used for the contention based random accessprocedure (first random access) and messages with the reference numbers#2-1 through #2-3 originally used for the non-contention based randomaccess procedure (second random access).

First of all, when the UE 20 generates uplink data and the bufferingunit 23 stores the uplink data (step B1 in FIG. 5), the UE 20 generatesand stores a random signature (Random Access Preamble) at the signaturemanaging unit 24 (step B2 in FIG. 5). Namely, the signature managingunit 24 has a function as creating means that creates a signature to beused for the contention based random access, which is executed whenuplink data destined for the eNB 10 is generated.

After that, the UE 20 creates a random access preamble message (uplinktransmission request) #1-1 containing the created signature at theaccess judging unit 25 and transmits the created message to the eNB 10from the antenna 21 via the transmitting/receiving unit 22 (step S1 a ofFIG. 3 and step B3 in FIG. 5).

Upon receipt of the uplink transmission request message #1-1, the eNB 10replies with a response message (Random Access Response) #1-2 responsiveto the received uplink transmission request message #1-1 (step S2 inFIG. 3) along with a timing advanced as synchronization message foruplink communication, an uplink grant for transmission permission, andothers. If a number of UEs 20 concurrently transmit requests through theRACH, the eNB 10 returns the response message #1-2 to the UEs 20.

Here, presuming that the eNB 10 could not recognize the uplinktransmission request message #1-1 that the UE 20 transmits becausedownlink data destined for the UE 20 arrived at the eNB 10 from theupper apparatus (i.e., the buffering unit 13 stores downlink data)before the transmission of the response message #1-2 (step A1 in FIG. 4)and the eNB 10 does not complete the receiving process on the downlinkdata.

In this case, the signature managing unit 15 of the eNB 10 creates andstores a signature (dedicated signature, the second information) thatthe UE 20 that is the destination of the downlink data uses for randomaccess (UL synchronization request) (step A2 in FIG. 4), and transmitsthe dedicated signature to the UE 20 through the use of a signatureallocation message (RA Preamble Assignment) #2-1 (step S1 b in FIG. 3and step A3 in FIG. 4).

When transmission of the uplink transmission request message #1-1 (stepS1 a in FIG. 3) and the signature allocation message #2-1 (step S1 b inFIG. 3) is completed, the eNB 10 cannot recognize “which UE 20 useswhich signature”. In other words, the eNB 10 cannot recognize that thetwo signatures (Random Preamble and Dedicated Preamble) are issued forwhich UE 20 because according to Non-Patent Document 2, either messagedoes not contain information (terminal ID) to identify the UE 20.

According to Non-Patent Document 2, since the terminal ID can becontained in a message (Scheduled Transmission) #1-3, the eNB 10 graspswhich UE 20 uses which signature after the receipt of the message #1-3from the UE (step S3 in FIG. 3).

Conversely, regardless of whether or not the UE 20 notifies the terminalID of the UE 20 itself to the eNB 10, when transmission of the uplinktransmission request message #1-2 (step S1 a in FIG. 3) and thesignature allocation message #2-1 (step S1 b in FIG. 3) is completed,both the random signature created by the UE 20 itself and the dedicatedsignature (Dedicated Preamble) allocated by the eNB 10 exist in the UE20, in other words, the UE 20 can recognize (detect) occurrence of thetwo kinds of random access.

If a number of signatures are issued for a single UE 20 as the abovecase, the UE 20 determines which signature is to be used. Specifically,when the UE 20 receives (allocation of) a dedicated signature from theeNB 10 from the step S2 (step B4 in FIG. 5), the access judging unit 25confirms, in cooperation with the signature managing unit 24, whether ornot multiple allocation of two signatures (preambles) occurs (step B5 inFIG. 5).

The confirmation concluded occurrence of multiple allocation (yes routein step B5), the UE 20 (the access judging unit 25) ignores thededicated signature allocated by the eNB 10 (step S1 c in FIG. 3 andstep B6 in FIG. 5), and selects the random signature created by the UE20 itself as an effective signature. In other words, the access judgingunit 25 has a function of selecting means which selects one between thetwo signatures. In addition, when no multiple allocation occurs, the UE20 determines the random signature created by the UE 20 itself to beeffective (no route in step B5).

Thereby, the random access procedure (contention based random accessprocedure) using the random signature created by the UE 20 becomeseffective, so that the UE 20 continues the contention based randomaccess procedure.

In other words, the UE 20 creates a message #1-3 and transmits themessage to the eNB 10 (step S3 in FIG. 3 and step B7 in FIG. 5). At thattime, the UE 20 grasps, through receiving the signature allocationmessage #2-1, that the downlink data destined for the UE 20 itselfarrives at the eNB 10, and therefore transmits the message #1-3 to theeNB 10 preferably after providing the message with information (such asan identifier or a flag) indicating that “the message #1-3 also servesas UL synchronization confirmation required for receiving downlinkdata”. UL synchronization confirmation is a confirmation response thatUL synchronization is secured because the UE 20 correctly receives ULtiming information contained in the message (Random access Response)#1-2.

In other words, UL synchronization request (third information), which istransmitted to the eNB 10 during the non-contention random access whichis however not selected, is a message to receive UL timing informationfrom the eNB 10 for UL synchronization, but the UE 20 already obtainsthe timing information during the contention based random access (#1-2).For the above, the UE 20 provides UL synchronization confirmationinforming eNB 10 of securing of UL synchronization to the message #1-3to be transmitted and then transmits the message #1-3.

However, as described above, since the eNB 10 recognizes the UE 20 towhich two signatures are allocated at the time of receiving the message#1-3, the eNB 10 can implicitly judge that the message #1-3 also servesas a UL synchronization request even when the identifier or a flag isnot explicitly provided.

Upon recognition of receiving the message (also serving as ULsynchronization confirmation) #1-3 (yes route of step A4 in FIG. 4), theeNB 10 judges in the judging unit 14 that the dedicated signatureallocated to the UE 20 is ignored in the same UE 20 (that is, the randomsignature created by the UE 20 is preferentially selected) andconsequently releases the dedicated signature allocated to the same UE20 in the signature managing unit 15 (step S3-1 in FIG. 3 and step A5 inFIG. 4).

Accordingly, the random access procedure (the non-contention basedrandom access procedure) using the dedicated signature allocated by theeNB 10 is halted, so that the dedicated signature allocated to the UE 20can be released during the random access procedure (at an early stage),which makes it possible to efficiently use signatures. Here, if themessage #1-3 is determined not to also serve as UL synchronizationconfirmation (no route in step S4), the downlink data does not arriveand only normal uplink communication occurs, so that the eNB 10transmits a message #1-4 (step A7).

The eNB 10 starts processing (control), such as scheduling of downlinkdata, based on the UL synchronization confirmation (third information)in the wireless resource managing unit 16 (step A6 in FIG. 4).

By receiving of the message (also serving as UL synchronizationconfirmation) #1-3, the eNB 10 can recognize that the response (RandomAccess Preamble) to the signature allocation message #2-1 from the UE 20can be omitted, so that unnecessary retransmission of the signatureallocation message #2-1 can be avoided. Further, reception of themessage #1-3 used for the contention based random access procedure,despite allocation of the dedicated signature, makes the eNB 10 possibleto recognize generation of uplink data at the UE 20.

Since the eNB 10 grasps the effective ID of the UE 20 through receivingthe message (also serving as UL synchronization confirmation) #1-3, sothat the eNB 10 can recognize that the contention occurred between whichUEs. The contention can be resolved by transmitting a ContentionResolution message #1-4 to the UEs 20 in question (step S4 in FIG. 3).

As described above, in the method of random access of the firstembodiment, even when uplink data and downlink data arrive in the sameUE 20, the UE 20 selects the signature the UE 20 itself created andthereby the contention based random access is continued. Consequently,the two kinds of random access procedure do not concurrently proceed fora single UE 20 until the last stage as denoted in FIG. 6. Accordingly,the control plane of the random access can be simplified and signaturesused for random access can be efficiently used. In addition, theinterference of the random access channel can be inhibited.

However, the two kind of random access procedure can be concurrentlyproceeded. Accordingly, for example, in the event that the message (ULsynchronization confirmation) #1-3 is contend with another UE, the UE 20recognizes occurrence of the contention with reference to the ContentionResolution message #1-4 notified from the eNB 10. In this case, sincecontinuation of the non-contention based random access may require atime to secure UL synchronization, the contention based random accesscan be concurrently executed through the use of a dedicated signatureallocated in the message #2-1 by eNB 10. However, the expiration periodof a dedicated signature for the UE 20 needs to be set to be long inthat case.

Since the information (UL synchronization confirmation) which istransmitted to the eNB 10 during the non-contention based random accessthat is not selected is transmitted to eNB 10 during the contentionbased random access, the reception processing of downlink data can besurely carried out along with the transmitting processing on uplinkdata.

Further, since the UL synchronization confirmation can be common to theuplink message #1-3 that is originally determined to be transmitted tothe eNB 10 during the contention based random access that is selected,there is no need to prepare (define) an unlink message dedicated to ULsynchronization confirmation, so that the wireless resource can beefficiently used.

Further, since the first embodiment can reduce the number of messagesthat are communicated between the eNB 10 and the UE 20 as compared witha second embodiment to be detailed below, it is possible to efficientlyuse the wireless resource and to shorten error recovery with the use ofretransmission control (HARQ: Hybrid Automatic Repeat reQuest).

(2) Second Embodiment

FIG. 7 is a sequence diagram illustrating a random access procedureaccording to the second embodiment; FIG. 8 is a flow diagram explainingthe operation of eNB 10 during the random access procedure of the secondembodiment; and FIG. 9 is a flow diagram explaining the operation of UE20 during the random access procedure of the second embodiment.

In the second embodiment, in the event of occurrence of multipleallocation of the preambles, the UE 20 ignores the signature (firstinformation) created by the UE 20 itself and selects the dedicatedsignature (second information) allocated by the eNB 10. Thereby, thenon-contention based random access procedure continues.

First of all, when uplink data arrive in the UE 20 and is stored in thebuffering unit 23 (step B11 in FIG. 9), the UE 20 creates and stores arandom signature (Random Access Preamble) at the signature managing unit24 (step B12 in FIG. 9), creates an uplink transmission request (RandomAccess Preamble) message #1-1 containing the signature at the accessjudging unit 25, and transmits the message #1-1 from the antenna 21 viathe transmitting/receiving unit 22 (step S1 a in FIG. 7 and step B13 inFIG. 9).

Upon receipt of the uplink transmission request message #1-1, the eNB 10replies with a response message (Random Access Response) #1-2 to thereceived uplink transmission request message (step S2 in FIG. 7) alongwith a timing advanced for synchronization signal for uplinkcommunication, an uplink grant for transmission permission, and others.If a number of UEs 20 concurrently transmit requests through the RACH,the eNB 10 returns the response message #1-2 to the UEs 20.

Here, also in the second embodiment presumes that the eNB 10 could notrecognize the uplink transmission request message #1-1 transmitted bythe UE 20 because downlink data destined for the UE 20 arrived at theeNB 10 from the upper apparatus (i.e., the buffering unit 13 storesdownlink data) before the transmission of the response message #1-2(step A11 in FIG. 8) and the eNB 10 does not complete the receivingprocess on the downlink data.

In this case, the signature managing unit 15 of the eNB 10 creates andstores a signature (dedicated signature) that the UE 20 that is thedestination of the downlink data uses for random access (ULsynchronization request) (step A12 in FIG. 8), and transmits thededicated signature to the UE 20 through the use of a signatureallocation message (RA Preamble Assignment) #2-1 (step S1 b in FIG. 7and step A13 in FIG. 8).

The UE 20, which receives the signature allocation message #2-1,transmits, to the eNB 10 through the RACH, a message (Random AccessPreamble) #2-2 containing the dedicated signature allocated by the eNB10. (step S2 a in FIG. 7).

Here, when transmission of the uplink transmission request message #1-1(step S1 a in FIG. 7) and signature allocation message #2-1 (step S1 bin FIG. 7) is completed, the UE 20 can recognizes the presence of boththe random signature created by the UE 20 itself and the dedicatedsignature allocated by the eNB 10.

Therefore, the UE 20 judges which signature is to be used. In otherwords, when the eNB 10 allocates a signature from step S2 (step B14 inFIG. 9), the UE 20 of the second embodiment confirms, in cooperationwith the signature managing unit 24, whether or not multiple allocationof two signatures (preambles) is occurring (step B15 in FIG. 9).

As a result, when multiple allocation is occurring (yes route in stepB15), the UE 20 ignores the random access signature created by the UE 20itself (the signature transmitted to the eNB 10) (step S1 d in FIG. 7and step B16 in FIG. 9), and selects the dedicated signature allocatedby the eNB 10 as an effective signature. When multiple allocation is notoccurring, the dedicated signature is made effective (no route in stepB15).

Consequently, the random access procedure (the non-contention basedrandom access procedure) through the use of the dedicated signatureallocated by the eNB 10 continues.

After that, the UE 20 creates the message #1-3 and transmits the createdmessage to the eNB 10 (step S3 in FIG. 7 and step B17 in FIG. 9).Concurrently, since also uplink data arrive, the UE 20 provides themessage #1-3 with information (an identifier or a flag) indicating thatthe message #1-3 also “serves as a message (UL scheduling request) torequest transmission (scheduling) of unlink data” by the identifierproviding unit 26 and transmits the message #1-3 to the eNB 10.

In other words, UL scheduling request (third information), which istransmitted to the eNB 10 during the contention random access, which isnot selected, is provided to the message #1-3 destined for the eNB 10and is transmitted to the eNB 10.

However, as described above, since the eNB 10 recognizes a UE 20 towhich two signatures are allocated at the time of receiving the message#1-3, the eNB 10 can implicitly judge that the message #1-3 from the UE20 also serves as a UL scheduling request even when the identifier or aflag is not explicitly provided.

Upon recognition of receiving the message (also serving as UL schedulingrequest) #1-3 (yes route of step A14 in FIG. 8), the eNB 10 judges thatthe UE 20 makes the dedicated signature allocated by the eNB 10 to theUE 20 effective, and releases the random signature which the eNB 10manages and which is received from the UE 20 in the signature managingunit 15 (step S3-2 in FIG. 7 and step A15 in FIG. 8).

Consequently, the random access procedure (the contention based randomaccess) through the use of the random signature created by the UE 20becomes ineffective (halts), so that the dedicated signature can bereleased during the random access procedure (at an early stage), whichmakes it possible to efficiently use signatures.

In the eNB 10, the wireless resource managing unit 16 carries outprocessing (control) of allocation of UL wireless resource in responseto the UL scheduling request (step A16 in FIG. 8). Since the secondembodiment makes the dedicated signature effective, there is no need totransmit Contention Resolution message #1-4 used for the contentionbased random access procedure to the UE 20 in question and therefore thetransmission can be halted (step S4 in FIG. 7 and step A17 in FIG. 8).In addition, if the eNB 10 judges that the message #1-3 does not serveas the UL scheduling request, the eNB 10 terminates the processing (noroute in step A14 in FIG. 8).

As described above, according to the method of random access of thesecond embodiment, even when uplink data and downlink data areconcurrently arrive in the same UE 20, the UE 20 selects the signatureallocated by the eNB 10 and thereby the non-contention based randomaccess is continued. Consequently, the two kinds of random accessprocedure do not concurrently proceed until the last. Accordingly, thecontrol plane of the random access can be simplified and signatures usedfor random access can be efficiently used. In addition, the interferenceof the RACH can be inhibited.

Since the information (UL scheduling request) which is transmitted tothe eNB 10 during the contention based random access that is notselected is transmitted to eNB 10 during the contention based randomaccess, the reception processing of downlink data can be surely carriedout along with the transmitting processing on uplink data.

Further, when the UL scheduling request to the eNB 10 is common to theuplink message #1-3, there is no need to prepare (define) an unlinkmessage dedicated to UL scheduling request, so that the wirelessresource can be efficiently used.

The first and the second embodiments assumes that the eNB 10 transmitsthe signature allocation request message #2-1 to the UE 20 after the UE20 transmits the uplink transmission request message #1-1. However, evenwhen these messages #1-1 and #2-1 are transmitted in the reverse order,multiple allocation also occurs so that it is sufficient that either oneof the signatures is made effective.

(2.1) First Modification

The above message also serving as UL scheduling request to the eNB 10may be a message (Random Access Preamble) #2-2 transmitted in step S2 ain FIG. 7 as denoted in the example FIG. 10.

In this case, the UE 20 needs not transmit the message #1-3 and canconsequently halt the transmission of the message #1-3 (step S3).Accordingly, unnecessary transmission of uplink messages can be avoidedso that efficiently use of uplink wireless resource (band) can beensured.

Since the eNB 10 cannot recognize (i.e., cannot manage) that which UE 20uses which preamble unless receives the message #1-3, there is no needto release the preamble (no need to carry out step S3-2 in FIG. 7).Consequently, it is possible to reduce the processing load of thepreamble management on the eNB 10.

(2.2) Second Embodiment

Further, alternative to transmitting the UL scheduling request to theeNB 10 during the non-contention based random access procedure, the ULscheduling request may be, as denoted in FIG. 11, transmitted along withthe response (ACK/NACK signal) responsive to the message #2-3 uponcompletion of the procedure (step S5 in FIG. 11). Further alternatively,the request may be transmitted in the form of an independent uplinkmessage after the transmission of the message #2-3.

(3) Third Embodiment

FIG. 12 is a sequence diagram illustrating a random access procedureaccording to the third embodiment; FIG. 13 is a flow diagram explainingthe operation of eNB 10 during the random access procedure of the thirdembodiment; and FIG. 14 is a flow diagram explaining the operation of UE20 during the random access procedure of the third embodiment.

Differently from the first and the second embodiments, description ofthe third embodiment presumes that uplink data arrive in the UE 20 undera state where a dedicated signature is allocated to the UE 20.

In other words, when downlink data which is destined for the UE 20 andwhich is transmitted from the upper apparatus arrives at the eNB 10(i.e., the buffering unit 13 stores downlink data) (step A21 in FIG.13), the eNB 10 creates and stores a signature (dedicated signature)(step A22 in FIG. 13) that is to be used for random access (ULsynchronization request) by the UE 20, the destination of the downlinkdata (step A2 in FIG. 13), and then transmits the created signature bymeans of a signature allocation message #2-1 (RA Preamble Assignment) tothe destination UE 20 through the transmitting/receiving unit 12 (stepA11 in FIG. 12 and step A23 in FIG. 13).

Upon receipt of the signature allocation message #2-1, the UE 20 storesand manages the dedicated signature allocated by the received message inthe signature managing unit 24 (step B21 in FIG. 14).

After that, when UE 20 generates uplink data and the buffering unit 23stores the uplink data (step B22 in FIG. 14), the UE 20 (the signaturemanaging unit 24) does not generates a random signature (step S12 inFIG. 12 and step B23 in FIG. 14) differently from the first and thesecond embodiments.

As the substitute, the UE 20 creates, in the access judging unit 25, anUL synchronization request (Random Access Preamble) message #2-2containing the dedicated signature allocated by eNB 10 and transmits thecreated message to the eNB 10 through the transmitting/receiving unit 22from the antenna 21.

At that time, because of the generation of the uplink message, the UE 20provides information (an identifier or a flag) indicating that “themessage also serves as an UL scheduling request” to the message #2-2 inthe identifier providing unit 26 and transmits the message to the eNB 10(step S13 in FIG. 12 and step B24 in FIG. 14).

In other words, the UE 20 additionally transmits the UL schedulingrequest to the eNB 19 (sic, correctly 10) in the event of executingrandom access through the use of a signature for obtaining(establishing) the uplink synchronization when downlink data isgenerated.

Upon confirmation of the reception of the message #2-2 (also serving asUL scheduling request) (yes route in step A24 in FIG. 13), the eNB 10causes the wireless resource managing unit 16 to control allocation ofthe UL resource corresponding to the UL scheduling request (step A25 inFIG. 13) and creates the signature managing unit 15 to create a responsemessage #2-3 to the message #2-2 and transmit the created message to theUE 20 (step S14 in FIG. 12). Conversely, since an UL synchronizationrequest message #2-2 not containing the UL scheduling request (no routein step A24 in FIG. 13) represents a case in which a normal uplink datacommunication is arriving, the eNB 10 transmits the message #2-3 withoutallocation of an UL resource (step A26 in FIG. 13).

As described above, according to the method of random access of thethird embodiment, after downlink data destined for a UE 20 arrive at eNB10 and responsively allocates a signature to the same UE 20, the UE 20does not generate a signature used for the contention based randomaccess, but does continue the non-contention based random access usingthe signature allocated by the eNB 10. Consequently, the two kinds ofrandom access do not concurrently proceed.

Accordingly, the control plane of the random access can be simplifiedand signatures used for random access can be efficiently used. Inaddition, both the UE 20 and the eNB 10 do not have to always manage thetwo kinds of signature.

Further, since, during the non-contention based random access,information (UL scheduling request), which is transmitted to the eNB 10during the contention based random access, is transmitted to the eNB 10,the transmitting processing of the uplink data can be surely carried outalong with the receiving processing of the downlink data.

Still further, the random access preamble message #2-2 also serves as anUL scheduling request, delay until the start of transmitting uplink datacan be reduced as compared with the following fourth embodiment (inwhich a confirmation response message to the random access responsemessage #2-3 also serves as the UL scheduling request).

(4) Fourth Embodiment

FIG. 15 is a sequence diagram illustrating a random access procedureaccording to the fourth embodiment; FIG. 16 is a flow diagram explainingthe operation of eNB 10 during the random access procedure of the fourthembodiment; and FIG. 17 is a flow diagram explaining the operation of UE20 during the random access procedure of the fourth embodiment.

Similarly to the third embodiment, the fourth embodiment presumes thatthe UE 20 generates uplink data under a state where a dedicatedsignature is previously allocated to the UE 20.

In other words, when downlink data which is destined for the UE 20 andwhich is transmitted from the upper apparatus arrives at the eNB 10(i.e., the buffering unit 13 stores downlink data) (step A31 in FIG.16), the eNB 10 creates and stores at the signature managing unit 15 asignature (dedicated signature) (step A32 in FIG. 16) that is to be usedfor random access (UL synchronization request) by the UE 20, thedestination of the downlink data, and then transmits the createdsignature by means of a signature allocation message #2-1 (RA PreambleAssignment) to the UE 20 through the transmitting/receiving unit 12(step S11 in FIG. 15 and step A33 in FIG. 16).

Upon receipt of the signature allocation message #2-1, the UE 20 storesand manages the dedicated signature allocated by the received message inthe signature managing unit 24 (step B31 in FIG. 17).

After that, UE 20 generates uplink data and the buffering unit 23 storesthe uplink data (step B32 in FIG. 17), the UE 20 (the signature managingunit 24) does not generate a random signature (step S12 in FIG. 15 andstep B33 in FIG. 17) differently from the first and the secondembodiments.

As the substitute, the UE 20 creates a message #2-2 (Random AccessPreamble) containing the dedicated signature allocated by eNB 10 in theaccess judging unit 25, and transmits the message to the eNB 10 throughthe transmitting/receiving unit 22 from the antenna 21 (step S13 in FIG.15 and step B34 in FIG. 17).

Upon recognizing reception of the message #2-2 (yes route in step A34 inFIG. 16), the eNB 10 causes the wireless resource managing unit 16 toallocate the UL wireless resource (step A35 in FIG. 16) and causes thesignature managing unit 15 to create a response message #2-3 to themessage #2-2 and transmit the created message to the UE 20 (step S14 inFIG. 15). Conversely, if the eNB 10 cannot recognize the reception ofthe message #2-2 (also serving as the UL scheduling request), the eNB 10terminates the process (no route in step A34 in FIG. 16).

On the other hand, upon receipt of the response message #2-3 from theeNB 10 (step B34 in FIG. 17), the UE 20 creates a confirmation response(ACK/NACK) message #3 to the response message #2-3 in the access judgingunit 25 and transmits the created message to the eNB 10. At that time,the UE 20 provides information (an identifier or a flag) indicating that“the message #3 also serves as an UL scheduling request” to theconfirmation response message #3 in the identifier providing unit 26 andtransmits the message to the eNB 10 (step 35 in FIG. 17). The providedinformation may be transmitted by a dedicated uplink messagealternatively to being transmitted concurrently with the confirmationresponse message #3.

In other words, when executing random access through the use of asignature for obtaining (establishing) the uplink synchronization, theUE 20 additionally transmits the UL scheduling request to the eNB 10when the random access terminates.

As described above, according to the method of random access of thefourth embodiment, when uplink data is generated in a UE 20 after theeNB 10 generates downlink data destined for the UE 20 and responsivelyallocates a signature to the same UE 20, the UE 20 does not create asignature used for the contention based random access but does continuethe non-contention based random access using the signature allocated bythe eNB 10, which thereby brings the same effects and advantages as thethird embodiment.

In addition, since the confirmation response message #3 to the randomaccess response message #2-3 also serves as an UL scheduling request, atleast transmission of downlink data can be normally started even if theeNB 10 cannot correctly receive or recognize the confirmation responsemessage #3 due to the propagation environment.

The uplink message also serving as an UL scheduling request may be, forexample, one for reporting the CQI to the eNB 10.

(5) Fifth Embodiment

FIG. 18 is a sequence diagram explaining a random access procedure ofthe fifth embodiment. This embodiment is an example of transmitting thesignature allocation message (RA preamble Assignment) #2-1 after thetransmission of Response message (Random Access Response) #1-2 to the UE20 from the eNB 10.

In other words, the UE 20 generates uplink data, the UE 20 creates arandom signature at the signature managing unit 24 and transmits arandom access preamble message (uplink transmission request) #1-1containing the created random signature to the eNB 10 (step S1 a).

Upon receipt of the message #1-1, the eNB 10 replay with the responsemessage (Random Access Response) #1-2 to the received uplinktransmission request message #1-1 (step S2) along with a timing advancedas synchronization signal for uplink communication, an uplink grant fortransmission permission, and others. If a number of UEs 20 concurrentlytransmit requests through the RACH, the eNB 10 returns the responsemessage #1-2 to the UEs 20.

At this stage, when downlink data which is destined for the UE 20 andwhich is from the upper apparatus arrives at the eNB 10, the eNB 10creates a dedicated signature in the signature managing unit 15, andtransmits the signature to the UE 20 via the signature allocationmessage (RA Preamble Assignment) #2-1 (step S2 b).

Upon receipt of the signature allocation message (RA PreambleAssignment) #2-1, multiple allocation occurs due to the presence boththe random signature and the dedicated signature at the UE 20. Whendetecting the multiple allocation, the UE 20 selects one signature andcontinues the execution of the random access corresponding to theselected signature (FIG. 18 assumes the contention based random accessis selected) in the same manner as the first and the second embodiments.

In this case, the uplink message #1-3 that is to be transmitted in thelater step S3 can also serve as UL synchronization confirmation the sameas the first embodiment. Alternatively, the uplink message #1-3 can alsoserve as the UL scheduling request the same as the second embodiment.Further, the uplink message (Random Access Preamble) #2-2 can also serveas the UL scheduling request, which may be transmitted by means of anACK/NACK signal responsive to the response message #2-3 or may betransmitted by means of a dedicated uplink message.

Then, the eNB 10 confirms the effective ID of the UE 20 by, for example,receiving the message #1-3 and can release one of the signatures in thestate of the multiple allocation.

Namely, from the first and the fifth embodiment, the signatureallocation message (RA Preamble Assignment) #2-1 may be transmitted atany timing as long as before the eNB 10 receives the message #1-3.

(6) Sixth Embodiment

FIG. 19 is a sequence diagram explaining a random access procedure ofthe sixth embodiment. This embodiment is an example of transmitting thesignature allocation message (RA preamble Assignment) #2-1 after thetransmission of a message (Scheduled Transmission) #1-3 to the eNB 10from the UE 20.

Specifically, when the UE 20 generates uplink data, the UE 20 transmitsthe random access preamble message (uplink transmission request) #1-1containing the random signature to the eNB 10 (step S1 a), receives aresponse message #1-2 to this message (step S2), and transmits themessage #1-3 (step S3).

Upon receipt of the message #1-3, the eNB 10 starts the detection of theeffective ID (terminal ID) of the UE 20. Successful detection of theeffective ID makes it possible to recognize that the contention ofsignatures occurs between which UEs 20. If a contention occurs, the eNB10 transmits the contention resolution message (Contention Resolution)#1-4 to the UEs 20 in question to solve the contention (step S4).

Here, presuming that the eNB 10 could not recognize the message #1-3 dueto the reason that during processing the message #1-3, downlink datadestined for the UE 20 arrives at the eNB 10 from the upper apparatus(the buffering unit 13 stores downlink data) and therefore the receivingof the message #1-3 could not be completed.

In this case, the eNB 10 causes the signature managing unit 15 to createand store a signature (dedicated signature: the second information) thatis to be used for random access (UL synchronization request) by UE 20,and transmits the dedicated signature via the signature allocationmessage (RA preamble Assignment) #2-1 to the UE 20 through thetransmitting/receiving unit 12 (step S3 a).

Upon completion of transmitting and receiving processing on thesemessages #1-3 and #2-1 the eNB 10 can recognize “which UE 20 uses whichsignature”, that is, can recognize “two signatures (i.e., RandomPreamble and Dedicated Preamble) are issued to which UE 20.

Here, when the UE 20 and another UE (hereinafter called the second UE)do not establish contention, the UE 20 can be judged to have multipleallocation, so that the eNB 10 (the signature managing unit 15)immediately releases the dedicated signature allocated to the UE 20, andnormally transmits a Contention Resolution message #1-4 (step S4). Atthis time, the uplink synchronization can correctly secured, so that thetransmission of downlink data can be started.

Conversely, when the UE 20 and the second UE establish contention, thereis a possibility of collision between messages #1-3 that the UE 20 andthe second UE transmit. At this stage, the UE 20 cannot be judged tohave multiple allocation, and the dedicated signature allocated to theUE 20 cannot be immediately released. In the event of contention, theeNB 10 notifies the UE 20 of the contention through the ContentionResolution message #1-4. This case preferably maintains the dedicatedsignature until an UE 20 having multiple signatures is detected.

In the meantime, regardless of whether or not the UE 20 notifies the eNB10 the terminal ID of the UE 20 itself to the eNB 10, the UE 20 canrecognize (detect) the presence of both the random signature (RandomPreamble) created in the UE 20 itself and the dedicated signatureallocated by the eNB 10, that is, occurrence of two kinds of randomaccess, when the transmission of the message #1-3 and the signatureallocation message #2-1 is completed.

At that time, when the messages #1-3 transmitted from the UE 20 and thesecond UE do not collide with each other, the UE 20 grasps that nocontention is established with reference to the Contention Resolutionmessage #1-4 notified from the eNB 10. Consequently, the UE 20, forexample, releases the dedicated preamble, and maintains ULsynchronization in the contention based random access procedure becausethe UE 20 correctly receives UL timing information via the message #1-2.

Conversely, when the messages #1-3 transmitted from the UE 20 and thesecond UE collide with each other, the UE 20 grasps that contention isestablished with reference to the Contention Resolution message #1-4notified from the eNB 10. Consequently, the UE 20 releases the dedicatedpreamble and can concurrently perform both the UL synchronizationrequest and the UL scheduling request in the contention based randomaccess the same as the first embodiment. Alternatively, the UE 20 canperform both the UL synchronization request and the UL schedulingrequest in the non-contention based random access the same as the secondthrough the fourth embodiments.

Further, as described in the first embodiment, both random accessprocedures can be concurrently proceed. In other words, upon detectionthat the contention is established, the non-contention based randomaccess can also be carried out at the same time through the use of thededicated signature notified in the message #2-1.

The sixth embodiment describes the case where the message #2-1 istransmitted during the message #1-3 is being processed. Needless to say,this embodiment results the same if the message #2-1 is transmittedbetween the messages #1-2 and #1-3.

The embodiments can selectively perform one among a number of kinds ofrandom access.

In addition, resources such as signatures to be used for the randomaccess can be efficiently used. In addition, the interference of therandom access channel (RACH) can be inhibited.

As detailed above, since the embodiments can selectively carry out oneamong a number of random access procedures and can efficiently useresource such as signatures used for the random access procedures, theembodiments seem to be extremely useful for the technical field of thewireless communication.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a illustrating of thesuperiority and inferiority of the invention. Although the embodimentshave been described in detail, it should be understood that the variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention

What is claimed is:
 1. A method for random access in a wirelesscommunication system including a base station and a wireless terminal,the method comprising: at the wireless terminal, recognizing a multipleallocation of random access preambles including a first random accesspreamble and a second random access preamble, the second random accesspreamble being received from the base station; and performing only onerandom access procedure among a first random access procedure using thefirst random access preamble and a second random access procedure usingthe second random access preamble, in a case of receiving a new requestrequesting for one random access procedure among the first random accessprocedure and the second random access procedure while another randomaccess procedure among the first random access procedure and the secondrandom access procedure is already ongoing.
 2. A wireless communicationsystem comprising: a base station; and a wireless terminal communicatingwith the base station, wherein the wireless terminal recognizes amultiple allocation of random access preambles including a first randomaccess preamble and a second random access preamble, the second randomaccess preamble being received from the base station, and performs onlya second random access procedure using the second random accesspreamble, in a case of receiving a new request requesting for one randomaccess procedure among a first random access procedure using the firstrandom access preamble and the second random access procedure whileanother random access procedure among the first random access procedureand the second random access procedure is already ongoing; and the basestation performs a data communication with the wireless terminal.
 3. Awireless communication system comprising: a base station; and a wirelessterminal communicating with the base station, wherein the wirelessterminal recognizes a multiple allocation of random access preamblesincluding a first random access preamble and a second random accesspreamble, the second random access preamble being received from the basestation; and continues only a first random access procedure using thefirst random access preamble in a case of receiving a new requestrequesting for a second random access procedure using the second randomaccess preamble while the first random access procedure is alreadyongoing; and the base station performs a data communication with thewireless terminal.
 4. A wireless communication system comprising: a basestation; and a wireless terminal communicating with the base station,wherein the wireless terminal recognizes a multiple allocation of randomaccess preambles including a first random access preamble and a secondrandom access preamble, the first random access preamble being receivedfrom the base station; and continues only a first random accessprocedure using the first random access preamble in a case of receivinga new request requesting for a second random access procedure using thesecond random access preamble while the first random access procedure isalready ongoing; and the base station performs a data communication withthe wireless terminal.
 5. A wireless communication system comprising: abase station; and a wireless terminal communicating with the basestation, wherein the wireless terminal recognizes a multiple allocationof information for random access including first information and secondinformation, the second information being received from the basestation, and selects the second information used for second randomaccess and only performs the second random access using the selectedinformation, in a case of receiving a new request requesting for onerandom access among first random access using the first information andthe second random access while another random access among the firstrandom access and the second random access is already ongoing; and thebase station performs a data communication with the wireless terminal.6. A wireless terminal comprising: a communication unit that receives asecond random access preamble, which is used for a second random accessprocedure, from a base station; and a processor that recognizes amultiple allocation of random access preambles including a first randomaccess preamble and the second random access preamble, and performs onlythe second random access procedure using the received second randomaccess preamble in a case of receiving a new request requesting for onerandom access procedure among the first random access procedure and thesecond random access procedure while another random access procedureamong the first random access procedure and the second random accessprocedure is already ongoing.
 7. A base station comprising: a signaturemanaging unit that manages a second random access preamble used for asecond random access procedure and allocates the second random accesspreamble for a wireless terminal; and a communication unit that performsa data communication with the wireless terminal which recognizes amultiple allocation of random access preambles including a first randomaccess preamble and the second random access preamble, the second randomaccess preamble being received from the base station, and performs onlythe second random access procedure using the allocated second randomaccess preamble, in a case of receiving a new request requesting for onerandom access procedure among a first random access procedure using thefirst random access preamble and the second random access procedurewhile another random access procedure among the first random accessprocedure and the second random access procedure is already ongoing. 8.A base station comprising: a signature managing unit that manages asecond random access preamble used for a second random access procedureand allocates the second random access preamble for a wireless terminal;and a communication unit that performs a data communication with thewireless terminal which recognizes a multiple allocation of randomaccess preambles including a first random access preamble and the secondrandom access preamble, the second random access preamble being receivedfrom the base station, and continues only a first random accessprocedure using the first random access preamble in a case of receivinga new request requesting for the second random access procedure usingthe allocated second random access preamble which is received from thebase station while the first random access procedure is already ongoing.9. A base station comprising: a signature managing unit that manages afirst random access preamble used for a first random access procedureand allocates the first random access preamble for a wireless terminal;and a communication unit that performs a data communication with thewireless terminal which recognizes a multiple allocation of randomaccess preambles including the first random access preamble and a secondrandom access preamble, the first random access preamble being receivedfrom the base station, and continues only the first random accessprocedure using the allocated first random access preamble in a case ofreceiving a new request requesting for a second random access procedureusing the second random access preamble while the first random accessprocedure is already ongoing.
 10. A base station comprising: a signaturemanaging unit that manages second information used for second randomaccess and allocates the second information for a wireless terminal; anda communication unit that performs a data communication with thewireless terminal which recognizes a multiple allocation of informationfor random access including first information and the secondinformation, the second information being received from the basestation, and selects the allocated second information used for thesecond random access, in a case of receiving a new request requestingfor one random access among first random access using the firstinformation and the second random access while another random accessamong the first random access and the second random access is alreadyongoing and only performs the second random access using the selectedinformation.
 11. A base station comprising: a signature managing unitthat manages a second random access preamble used for a second randomaccess and allocates the second random access preamble for a wirelessterminal; and a communication unit that performs a data communicationwith the wireless terminal which, when the wireless terminal receives arequest for transmitting the allocated second random access preambleused for the second random access during performing first random accessusing a first random access preamble, the second random access preamblebeing received from the base station, recognizes a multiple allocationof random access preambles including the first random access preambleand the second random access preamble and only performs the secondrandom access.
 12. A base station comprising: a signature managing unitthat manages a first random access preamble used for a first randomaccess and allocates the first random access preamble for a wirelessterminal; and a communication unit that performs a data communicationwith the wireless terminal which, when the wireless terminal receives arequest for transmitting a second random access preamble used for secondrandom access during performing the first random access using theallocated first random access preamble, the first random access preamblebeing received from the base station, recognizes a multiple allocationof random access preambles including the first random access preambleand the second random access preamble and only performs the first randomaccess.